The present invention is directed to intraocular lenses (IOLs). More particularly, the invention relates to IOLs which have a plurality of optical powers and, in addition, are adapted to provide accommodating movement in the eye.
The human eye includes an anterior chamber between the cornea and iris, a posterior chamber, defined by a capsular bag, containing a crystalline lens, a vitreous chamber behind the lens containing the vitreous humor, and a retina at the rear of this chamber. The human eye has a natural accommodation ability. The constriction or contraction and relaxation of the ciliary muscle provides the eye with near and distant vision, respectively. This ciliary muscle action shapes the natural crystalline lens to the appropriate optical configuration for focussing light rays entering the eye on the retina.
After the natural crystalline lens is removed, for example, because of cataract or other condition, a conventional, monofocal IOL can be placed in the posterior chamber. Such a conventional IOL has very limited, if any, accommodating ability. However, the wearer of such an IOL continues to require the ability to view both near and far (distant) objects. Corrective spectacles may be employed as a useful solution. Recently multi-focal IOLs without accommodating movement have been used to provide vision correction.
Attempts have been made to provide IOLs with accommodating movement along the optical axis of the eye as an alternative to shape changing. Examples of such attempts are set forth in Levy U.S. Pat. No. 4,409,691 and several patents to Cumming, including U.S. Pat. Nos. 5,674,282 and 5,496,366. The disclosure of each of these patents is incorporated herein by reference. One problem that exists with IOLs which are adapted for accommodating movement toward and away from the retina of the eye is that such IOLs often cannot move sufficiently to obtain the desired accommodation because of space constraints within the eye. The present inventors are unaware of any so-called accommodating IOL which provides the desired degree of accommodation.
It would be advantageous to provide IOLs adapted for accommodating movement which can achieve an increased amount of accommodation with readily attainable amounts of accommodating movement.
New accommodating IOLs have been discovered. The present IOLs provide enhanced accommodation with a relatively limited, and readily attainable amount of accommodating movement. The present accommodating IOLs take advantage of one or more components and/or other features of the eye to provide for the accommodating movement. For example, accommodating movement can be provided by action of the ciliary muscle of the eye and/or of the zonules of the eye and/or by the vitreous pressure within the eye. Further, the optic or lens body of the IOL has a plurality of different optical powers, that is it is multifocal. Such lens body can be refractive or diffractive.
The combination of an IOL which is adapted to cooperate with the eye to provide accommodating movement and a multifocal lens body provides substantial advantages. For example, the multifocal lens body allows substantially enhanced effective or apparent accommodation with a readily attainable amount of accommodating movement in the eye. By providing an IOL having a near vision correction power, as well as an intermediate and/or baseline and/or far vision correction power, enhanced apparent accommodation, for example, on the order of about 3.5 diopters of accommodation, particularly for viewing near objects, is readily obtained with relatively limited amounts of accommodating movement of the IOL. In addition, the accommodating movement of the present IOLs preferably provides for enhanced intermediate vision and an advantageously greater range of near vision as compared with current multifocal IOLs which are not adapted for substantial accommodating movement. The present IOLs are straightforward in construction, employ conventional or standard IOL materials of construction, are easy to produce and implant in the eye and provide outstanding results.
In one broad aspect of the invention, IOLs are provided which comprise a lens body sized and adapted for placement in a mammalian, for example, human, eye. This lens body has a plurality of different optical powers, that is the lens body is multifocal. The IOLs further include a movement assembly which is joined to the lens body of the IOL. The movement assembly is adapted to cooperate with the mammalian eye to effect accommodating movement of the lens body in the eye. Thus, the wearers of the present IOLs are provided with accommodation benefits obtained from the multifocal lens body and accommodating movement of the lens body.
In one useful embodiment, the lens body has a first optical power for near vision and a second optical power for far vision. Optionally, the transition between the near vision optical power and the far vision optical power may be progressive. The lens body may have a third optical power intermediate between the first and second optical powers.
The lens body preferably includes a plurality of different regions each having a different optical power. In one very useful embodiment, the lens body includes a plurality of annular zones extending radially outwardly from the central or optical axis of the lens body. The lens body of the present IOLs can have the optical characteristics of the optics of Portney U.S. Pat. Nos. 4,898,461 and 5,225,858, the disclosure of each of which is incorporated by reference herein.
The movement assembly preferably is adapted to cooperate with the ciliary muscle and/or the zonules of the mammalian eye and/or with the vitreous pressure in the eye to effect accommodating movement of the lens body in the eye. More preferably, the movement assembly is adapted to cooperate with the ciliary muscle and/or zonules of the mammalian eye and/or with the vitreous pressure in the eye to move the lens body toward a first position relative to the retina of the eye, for example, when the ciliary muscle is relaxed, and toward a different second position, for example, when the ciliary muscle is constricted or contracted. The first position of the lens body preferably enhances far vision whereas the second position of the lens body preferably enhances near vision. In one embodiment, the movement assembly comprises at least one biasing member, and preferably a plurality of biasing members, coupled to the lens body. The biasing member can be a spring or similar element. The movement assembly can be as disclosed in Levy U.S. Pat. No. 4,409,691, noted previously.
The movement assembly may comprise at least one fixation member, and preferably a plurality of fixation members, including a proximal end region coupled to the lens body and a distal end region extending away from the lens body and adapted to contact a capsular bag, for example, the posterior capsular bag, of the mammalian eye. In this embodiment, the action of the eye, for example, the ciliary muscle and/or the zonules, preferably acts directly on the fixation member or members which transfer the force to the lens body causing the accommodating movement of the lens body. A representative movement assembly including fixation members is set forth in the above-noted Cumming patents. One or more different approaches can be employed to couple the distal end region of the fixation member to the capsular bag. Examples of such approaches include the use of adhesives, fibrosis of the capsular bag, suturing and the like surgical techniques, and combinations thereof. If fixation member or members are used to transfer the force of the eye to the lens body to effect accommodating movement, preferably the fixation member or members are secured, more preferably fixedly secured, to the eye, and in particular, to the capsular bag of the eye.
In another broad aspect of the present invention, combination lens systems are provided which include an IOL, as discussed above, including a multifocal lens body and a movement assembly; and, in addition, a lens element adapted for implantation in the eye; preferably in a substantially fixed position in the eye, for example, adapted for implantation in the capsular bag of the eye, more preferably in contact with the capsular bag, for example, the posterior capsular bag or the equator of the capsular bag, of the eye.
The lens element preferably is adapted to reduce cell growth in the posterior capsular bag in the space defined by the capsular bag of the eye. Thus, the lens element is effective in reducing secondary opacification which may occur as the result of the implantation of the IOL.
Each of the lens body and the lens element of the above-noted lens combination has an optical axis and a maximum cross sectional area perpendicular to the optical axis. The lens element may have a larger or smaller maximum cross sectional area perpendicular to the optical axis than does the lens body. The relatively large or wide lens element facilitates inhibiting the growth of cells in the space formed by the capsular bag. Such inhibition preferably is sufficient to allow the multifocal lens body to effectively provide the desired vision correction to the wearer of the lens combination without substantial interference from such cell growth. The lens element preferably has a single optical power. Preferably, both the intraocular lens and the lens element of the combination are adapted for implantation in the posterior capsular bag of the mammalian eye with the lens body being located anterior of the lens element. To provide an enhanced degree of stability between the IOL and the lens element, one or more filaments or other structure(s) may be located between the lens body and lens element to facilitate substantial alignment between these two components.
Any feature or combination of features described herein is included within the scope of the present invention provided that the features of any such combination are not mutually inconsistent.
Additional aspects and advantages of the present invention are set forth in the following description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.